Prior art valves for controlling or regulating fluids are known, which include a valve body and a linear valve drive formed separate from the valve body, to which the valve body can be connected, in order to form the valve. The linear valve drive typically includes a drive unit which can shift an axially shiftable actuating element on which a valve closing element typically is provided or integrally molded. The drive unit can move the actuating element together with the valve closing element into a closed position, in which the valve closing element rests on a valve seat formed in the valve body and seals the same, so that no fluid can flow through the valve.
One problem consists in that the tight closing force of the valve can be reduced when the linear valve drive is switched off or is switched powerless. This problem also can occur when the components of the linear valve drive expand for example due to thermal changes, which causes a drive system that was exactly matched previously to have larger tolerances, which can lead to a reduced tight closing force.
Another problem consists in that the linear valve drive or its drive unit gets jammed or blocked, when the actuating element is shifted into its closed position. This occurs in particular when the drive unit is overloaded. This can be the case, for example, when the actuating element is moved against a stop such as the valve seat or an internal stop in the drive system.
From EP 2 222 524 B1 a solenoid valve is known, which includes a setting spring for setting a pretensioning force and a regulating spring, which act against each other, in order to provide a cumulative spring force of the spring drive, with which a valve tappet of the solenoid valve is shifted. Both springs have a constant spring rate, so that the cumulative spring force also has a constant spring rate along the compression path.
It is the object of the invention to provide a linear valve drive and a valve, respectively, with a simple, reliable and inexpensive construction which prevents blocking of the linear valve drive and with which the required tight closing force can be maintained when the linear valve drive is switched off.